|Event|Performance|Athlete|Nation|Place|Date|
|---|---|---|---|---|---|
|100 m|9.72|Usain Bolt|Jamaica|New York City NY, USA|May 31|
|100 m|9.69|Usain Bolt|Jamaica|Beijing, China|August 16|
|200 m|19.30|Usain Bolt|Jamaica|Beijing, China|August 20|
|4 x 100 m relay|37.10|Nesta Carter Michael Frater Usain Bolt Asafa Powell|Jamaica|Beijing, China|August 22|
|110 m hurdles|12.87|Dayron Robles|Cuba|Ostrava, Czech Republic|June 12|
|50 km race walk|3:34:14|Denis Nizhegorodov|Russia|Cheboksary, Russia|May 11|
|Marathon|2:03:59|Haile Gebrselassie|Ethiopia|Berlin, Germany|September 28|

Question: what is the number of countries listed in the table
Answer: 4